Computerized Labyrinth Solver Gregory Schallert Chad Craw

System Overview Motors Control Playing Platform by Video feedback. Video processing is done by the PC Motor control is done by the HC12

User Interface Minimal amount of buttons and LEDs The interface shall report current operating status, and any encountered errors through LED codes

User Interface Buttons AnalyzeStartStop Status LEDs Error LEDs

System Test on Startup The system will rotate the maze surface a maximum deflection on both axes All status and Error LEDs will flash in unison to make sure the are operational The system will analyze the current maze structure, and output a binary stream representing the wall placements as well as values of the current X and Y axis rotation to the Serial interface.

Dynamic Maze Construction Maze walls are placed in arbitrary positions to create a new maze each time. Limited Start and End “Tags” are placed along the outer edge of the wall

Maze Construction Diagrams … … … Notches for the wall segments Wall Segment Notches for Start and End tabsMaze Surface Contact Nodes Wall Slot Wall Segment Contact Nodes

Maze Scanning Phase An array of multiplexers are attached to the contact nodes of each wall slot. These connections are scanned synchronously by the HC12 board to determine positions of walls. Once this scan is complete, the virtual maze is passed to the connected PC via the serial interface to start the maze solving algorithm Ang X: 1.2 Ang Y: 5.5 X Pos:01 Y Pos:54

Lee Moore Algorithm Inputs: Walls, Start and End Points. Output: Finds the a path from start to finish. Each cell is given a value of -1. Starting Cell is given a value of 0 If we have not reached the end, set the current cell to the highest value not yet used. Each cell touching the current cell with a -1 has the value of this cell + 1 Check each cell to see if we are at the end If not, continue

Video Capture Use the CCD Camera to find ball location Compare the current location to the desired path Send the offset to the next goal to the serial interface

The Camera Logitech QuickCam® CCD Camera 352x288 Maximum True Resolution 30 Frames/sec 25cm/120 = 2mm grid 25cm/288 = < 1mm grid We want 4mm resolution MEANS WE ARE GOOD TO GO

The Software OpenCV Video Tracking algorithms DirectShow Video Capture Filters Logitech SDK Camera Calibration and Windows Drivers All of the Software is Free and Documented

The Process DirectShow captures the video input The OpenCV algorithms are applied to track the object The information is sent to the HC12 Any additional text overlays are added and rendered to the screen

A System Model Sum the masses Sum the Torques Solve for acceleration This relates the acceleration to the angle of the platform

A System Model (con’t) Take two snapshots One at the zero position One after some time Note R and d stay constant Use law of cosines to solve for the angle This relates the acceleration to the distance the control axle at r has turned Can also solve for vertical displacement

Control System The algorithms for the control system shall operate on the HC12 board. The system will collect feedback data from the Video tracking algorithm on the PC via the Serial Interface of the HC12 board This data shall be sent as a 3-byte packet at every sample interval of the tracking system It shall contain a signal start byte (to maintain alignment), followed by 2 data bytes for the current X and Y offsets The position of the ball while traversing the maze shall be maintained with a Fuzzy Logic Control system. The only data that needs to be collected from the PC Video tracking system is the ball’s current offset from its target position

Control System The FLC will use a rule set based on 5 states of the system: The ball is far to the left(top) of its target position The ball is near to the left(top) of its target position The ball is at its target position The ball is near to the right(bottom) of its target position The ball is far to the right(bottom) of its target position These rules shall be applied symmetrically to both the X and Y axes of the ball’s position. Using this rule-set, the control system shall derive the angular rotation necessary to move the ball in the desired direction at the desired speed.

Control System (Pathfinder) Start X Y Y offset = 20 X offset = 0 Y offset = 10 X offset = 0 Y offset = 0 X offset = 10 End Y offset = 0 X offset = 0

Motor Control Each motor shall be attached to the actuators of each axis, and shall operate independently of one another. The operation of each motor is identical due to the symmetrical nature of the maze surface.

Motor Specs SL561 Standard, BB Size: Length1.51” Width0.73” Height1.37” Torque46.1 oz Speed0.18 sec/60° Weight1.50 oz Voltage4.8V – 6V

Possible Errors Nonlinear elements of the system Fuzzy Logic Control Keep speed Down Video Resolution/timing Damp the system Keep speed Down

Conclusion